This application is based on and incorporates herein by reference Japanese Patent Application No. 2002-142745 filed on May 17, 2002.
The present invention relates to a semiconductor device package in which a device mounted on a resin casing is electrically connected to a lead insert molded in the resin casing using a bonding wire.
A proposed semiconductor device package of FIG. 8 is manufactured by: forming a resin casing 20 by injecting resin into a mold, in which a lead frame has already been placed; mounting a sensor device 10; and electrically connecting the sensor device 10 to each lead 40 of the lead frame at the bonding surface 41 thereof by wire bonding using bonding wires 50. For example, the sensor device 10 includes a diaphragm-type semiconductor pressure sensor chip 11 and a stage.12 as a single unit. The sensor chip 11 is bonded to the stage 12, and the sensor device 10 is fixed onto a device-mounting surface 21 of the resin casing 20 using, for example, an adhesive.
As shown in FIG. 9A, after a resin casing 20 is formed using a mold K1, the resin casing 20 is released from the mold K1 by pushing the resin casing 20 with a movable ejector pin P1 of the mold K1 along the direction shown with an arrow in the circular area AA. In this instance, as shown in FIG. 9B, flashes B1 are formed on a device-mounting surface 21 of the resin casing 20, at which the resin casing 20 is pushed by the movable ejector pin P1. The flashes B1 are unavoidable because the flashes B1 are formed by the resin seeping into the clearance between the ejector pin P1 and the mold K1, which is needed for allowing the ejector pin P1 to smoothly move.
There are demands that the resin casing 20 be as small as possible. Therefore, it is not possible to provide dedicatedly an area at which the resin casing 20 is pushed by the ejector pin separately from the device-mounting surface 21. For this reason, the resin casing 20 has been pushed by the ejector pin P1 at an area close to the lead frame or on the device-mounting surface 21 of the resin casing 20 when the resin casing 20 is released from the mold K1.
However, if an area near the lead frame is pushed by the ejector pin P1 for releasing the resin casing 20, the lead frame becomes tilted to worsen in flatness or lift off from the resin casing 20. As a result, the subsequent wire bonding process becomes adversely affected. On the other hand, if the device-mounting surface 21 is pushed by the ejector pin P1 for releasing the resin casing 20, flashes B1 are created on the device-mounting surface 21, and, as shown in FIG. 10, the sensor device 10 subsequently gets mounted over the flashes B1. As a result, the sensor device 10 becomes tilted when mounted, and wire bonding is no longer possible without removing the flashes B1. For this reason, an extra step is needed to remove the flashes B1 after the resin casing 20 is molded, despite the added work.
The inventors of the present invention have studied this issue and have prototyped a semiconductor device package of FIGS. 11A and 11B. In the device package of FIGS. 11A and 11B, a resin casing 20 has a recessed 21a in a device-mounting surface 21. When the resin casing 20 is released from a mold in its manufacturing process, the resin casing 20 gets pushed by an ejector pin at the bottom of the recess 21a. As a result, as shown in FIG. 11B, flashes B1 are confined in the recessed 21a, and the sensor device 10 of the device package of FIGS. 11A and 11B would not come in contact with the flashes B1. Consequently, the sensor device 10 would no longer tilt due to the flashes B1.
However, if a bonding pad 15 is located above the recessed 21a, another problem arises as described below. When the bonding pad 15 is wire bonded, a bonding tool presses a wire 50 to the pad 15 using ultrasonic vibration. Since the sensor device 10 is lifted above the resin casing 20 at the portion right above the recessed 21a, the sensor device 10 could tilt or shift during the wire bonding. As a result, the ultrasonic power to be used for the wire bonding may get dissipated, and the wires 50 may not be properly bonded. That is, preferable wire bondability may not be secured at the bonding pad 15.
Each bonding surface 41 of the leads 40 needs to be exposed from the resin casing 20 because the leads 40 are wire bonded at the bonding surfaces 41. However, if a mold resin seeps onto and attaches to the bonding surfaces 41 when the lead frame is insert molded, preferable wire bondability may not be secured at the bonding surface 41, either.
Thus, a semiconductor device package, in which a device mounted on a resin casing is,electrically connected to a lead insert molded in the resin casing with a bonding surface exposed using a bonding wire, has the above problems with wire bonding, if a bonding pad is located right above a recess as in the proposed semiconductor device package of FIGS. 11A and 11B or if a mold resin seeps onto and attaches to a bonding surface of a lead when a lead frame, from which the lead is formed, is insert molded.
The present invention has been made in view of the above aspects with an object to enhance the wire bondability in a semiconductor device package in which a device mounted on a resin casing is electrically connected to a lead insert molded in the resin casing using a bonding wire.
To achieve the object, a first semiconductor device, package according to the present invention includes a semiconductor device, a resin casing, a plurality of leads, and a plurality of bonding wires. The semiconductor device includes a plurality of bonding pads. The resin casing has a device-mounting surface. The device-mounting surface has a recess. The semiconductor device has been mounted on the device-mounting surface. Each of the leads has a bonding surface. Each of the leads has been insert molded in the resin casing such that the bonding surface is exposed from the resin casing. Each of the bonding wires electrically connects each of the bonding pads and each of the bonding surfaces. Each of the bonding pads and the recess have a positional relation such that the semiconductor device is supported by the device-mounting surface right below the bonding pads when the bonding pads are wire bonded using the bonding wires. Therefore, it is possible to prevent the semiconductor device from tilting or shifting when the bonding pads are wire bonded using the bonding wires.
To achieve the object, a second semiconductor device package according to the present invention includes a semiconductor device, a resin casing, a lead, and a bonding wire. The semiconductor device includes a bonding pad. The resin casing has a device-mounting surface. The semiconductor device has been mounted on the device-mounting surface. The lead has a bonding surface and a burr. The bonding wire electrically connects the bonding pad and the bonding surface. The burr is located at an edge of the bonding surface. The burr has functioned as a barrier to prevent a molten resin from seeping onto the bonding surface when the lead frame has been insert molded in the resin casing.